Objective: The EQ-5D is a standardized, nondisease-specific instrument for evaluating patients' preference-based valuations of health-related quality of life (HRQoL). This study's purpose was to determine the psychometric properties of EQ-5D in patients with irritable bowel syndrome (IBS).
Methods: Data from four European IBS studies were assessed: UK (n = 161 and n = 297), Spain (n = 503), and Germany (n = 100). The EQ-5D is a five-item health state descriptive system used to develop health states (EQ-5D(INDEX)) and a visual analog scale (VAS) (0-100 from worst to best imaginable health state, EQ-5D(VAS)). Measures used with the EQ-5D included the SF-36, Irritable Bowel Syndrome--Quality of Life (IBS-QOL), and both subjective and clinical global assessments of IBS. Convergent validity was assessed using SF-36 and IBS-QOL data, discriminant validity using global ratings of IBS severity, and responsiveness by subjective and physician assessment of condition.
Results: Moderate-to-high associations (r >or= 0.33) were seen between the EQ-5D(VAS) and the SF-36 and IBS-QOL subscales. Mean response scores to EQ-5D(INDEX) dimensions and the EQ-5D(VAS) score were significantly better for control patients than for patients with IBS (all P < 0.01). The EQ-5D(VAS) was able to discriminate between levels of pain severity (quartiles, P < 0.001; mild/moderate/severe, P < 0.05) and general health severity (mild/moderate/severe, P < 0.001). The EQ-5D(VAS) and the EQ-5D(INDEX) were responsive in patients using both a self-perceived (Subject's Global Assessment) and physician-rated (Clinic Global Assessment) improvement.
Conclusions: The EQ-5D performs well in comparison to general and disease-specific outcomes. It is a valid and responsive measure that can be used to generate preference-based valuations of HRQoL in patients with IBS and useful for comparisons in clinical and cost-effectiveness studies.